Intuition:
*We treat each internal page as a tree node
*Each node can have multiple linked children or none
*Taking the above picture as an example, the homepage is the first tree node that we will be given as an input to our function, and it has 4 children: page 1, page 2, page 3, and page 4
*Given the above idea, we have built 2 following algorithms to find all internal links of a web page with 2 given user inputs: homepage url and depth